Corrosion inhibitor and method of using the same



, wire.

United States Patent This invention relates to compositions and processes for preventing the corrosion of metals by aqueous liquids.

More particularly, the invention relates to compositions and methods for inhibiting the .corrosivity of aqueous fluids containing dissolved salts and gases to corrodible metals such as ferrous metals, copper, and copper alloys.

The corrosive effect of aqueous liquids on ferrous metals, copper, and copper-containing alloys due to the combined action of the water and other contaminants is well known and many expedients to eliminate or counteract this etfect have been proposed. Factors such as temperature, aeration, dissolved solids, and pH have been found to influence corrosion rates greatly. For example, it has been found that for each F. rise in temperature, corrosion rates of copper-containing alloys doubled. The corrosion rate of copper and ferrous metals would be affected similarly. The presence of dissolved solids such as chlorides, sulfates, sulfites, and bisulfates'have a marked effect on the rate of corrosion. Furthermore, dissolved gases, such as oxygen, hydrogen sulfide, carbon dioxide, and chlorine, either alone or in combination, have a deleterious effect on the metals listed above.

Corrosion is an important economic factor in industry and its prevention is often necessary and always desirable. For example, the prevention of corrosion in the papermaking industry, particularly the prevention of corrosion of the copper alloy wire cloths used with Fourdrinier papermaking machines, can double the useful life of these wires in some instances. A considerable amount of wire life research has been conducted in reference to Fourdinier papermaking machines. These studies reveal that the main factors influencing the useful life of such cloths are actual damage to the wire, mechanical wear, and corrosion. These factors may act alone or in combination with each other.

In addition to damage and mechanical wear, several types of corrosion of copper alloys have been found to be important in affecting the useful life of a Fourdrinier wire. These types are:

(1) Direct surface corrosion in which the surface of the shute and warp Wires are rather uniformly corroded, resulting in a loss of diameter. Generally, the brass shute wire corrodes more rapidly than the bronze Warp wires. Surface corrosion results in a rather uniform etching of the surface which is sometimes associated with tarnish or discoloration.

(2) Galvanic or bimetallic-corrosion is caused by the electric current resulting when two different metals or alloys are coupled. This situation exists between the bras's shute and the bronze warp and, under certain conditions, the brass shute will corrode quite rapidly. Seam corrosion would apparently fall into this category.

(3) Pitting and dezincification usually are associated with a copper sulfide film formation on the surface of the When such films are broken or become porous, localized corrosion takes place resulting in loss of metal, thereby, forming depressions or pits. Loss of zinc from the brass shute often occurs under these surface films. Impingement pitting results from the turbulent flow of a liquid over a metal surface leaving elongated pits.

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(4) Corrosion fatigue and intergranular corrosion seem to be related. Corrosion lowers fatigue resistance, and the presence of fatigue stresses tend to increase corrosion. Intergranular corrosion causes embrittlement.

Because of the vital function served by the Fourdrinier wire cloth in the papermaking operation, and because it is extremely susceptible to mechanical stresses, abrasion, and other deleterious influences, the wire cloth must be protected from lumps of furnish that may accumulate between the various rolls and the wire cloth and distend the wire cloth. The means most frequently adopted for this purpose is that of providing water showers located at various positions relative to the wire cloth to wash and remove any lumps of furnish that may have collected uponthe wire cloth and the wire return rolls. In one method of .retarding or. eliminating the corrosion of 'Fourdrinier wire cloths, the inhibitor is added to the water "accomplished. If the additionof the inhibitor is on a continuous basis, the surface of the wire is continuously exposed to the inhibitor solution. In some instances 'intermittent'addition of the inhibitor to the wire shower system gives excellent corrosion control and extended wire life. Another rnethod of treating the wire involves the addition of the inhibitor to the mass of paper pulp and water which ultimately comes into contact with the Fourdrinier wire.

The compound Z-mercaptobenzothiazole or its, salts either alone or in combination with other organic or inorganic corrosion inhibitors have been used to protect equipment constructed from either copper or copper-containing alloys from corrosion. When these same inhibitors were used in the papermaking industry to protect Fourdrinier wires, the results were not entirely satisfactory. For example, these inhibitors afiord inadequate protection against the effect of dissolved gases, such as hydrogen sulfide. These inhibitors also fail to coatthe Fourdrinier Wires with a lubricating film which is necessary to prevent excessive mechanical wear. In addition, many of the additives that have been'proposed for use with 2-mercaptobenzothiazole are not compatible with certain other chemicals present in the papermaking system.

Another example Where corrosion is important economically is in the oil burning industry. In the production of oil,.corrosion of steel and other metal well equip mentis caused by the action'of water and natural brines, which contain dissolved sulfides and/or carbon dioxide.

Corrosive sulfide brines may contain alkali and alkaline earth metal sulfides and hydrogen sulfide. Hydrogen sulfide is very soluble in water, brines, and crude oil and forms corrosive solutions which cause a deterioration of well and surface equipment. This corrosion takes place in both acidic and alkaline brines.

Corrosion in waterflood systems is also an important factor in oil production. Reference is hereby'made to the paper by L. C. Case entitled Will Corrosion Eat Up the Water-Flood Profit? in The Oil and Gas Journal, p. 76, January 16, 1961, for a discussion as to the causes and extent of corrosion in such systems. This article discusses chemical corrosion due to the action of dissolved oxygen, hydrogen sulfide and carbon dioxide and corconcerning the fundamental mechanism, there is agreement that corrosion in waterflood systems is a major problem.

It is an object of our invention to provide a composition that will, 'when it is added to an aqueous corrosive fluid in small amounts, materially inhibit the corrosive action of such a fluid.

Another object of the present invention is to provide a composition which when applied to wire cloths used on Fourdrinier papermaking machines acts as an anti-wear or wear-inhibiting agent, and thereby extends the useful life of such cloths in papermaking machines.

Other objects and advantages of the invention will become apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

Broadly stated, the corrosion of copper, copper alloys, and ferrous metals in contact with an aqueous system containing dissolved corrosive compounds is inhibited by adding to such an aqueous system a mixture comprising an alkali metal salt of Z-mercaptobenzothiazole and an N,N-dimethylamide of a straight chain unsaturated carboxylic acid.

As one example, the combination of alkali metal salts of Z-mercaptobenzothiazole and the,N,N-dimethylamides of long chain unsaturated fatty acids affords excellent protection to the treated Fourdrinier wires. Wires treated with thercompositions of this invention are resistant to the formation of copper sulfide by the reaction of hydro gen sulfide with the wires. The wires are coated with a sufficient quantity of the composition so that the wire is effectively lubricated and the wire is, protected against the effect of oxidizing corrosive agents because the 2-mercaptobenzothiazole will serve as an anti-oxidant While it is being converted into the disulfide, benzothiazolydi- 2 C-SH [O] Compositions made in accordance with this invention are stable solutions which can be easily handled and fed into the system being protected with metering pumps. These compositions when diluted with water yield stable emulsions with an only slightly alkaline pH. These dilute water solutions do not foam and actually impart defoaming action to papermill systems. Since the amides used are nonreactive and very stable to hydrolysis, these compositions are compatible with most chemicals used in papermill systems. In addition, these compositions act as detergents and as solvents to pitch which is a troublesome component of some pulps used in papermills.

Before proceeding with specific examples illustrating our invention, it may be well to indicate in general the nature of the materials required in the process.

Any of the alkali metal salts of Z-mercaptobenzothiazole may be used in the process of our invention. Examples of specific salts which are preferred because of cost and availability include the sodium and potassium salts.

Suitable N,N-dimethylamides of straight chain carboxylic acids are those prepared from carboxylic acids containing 18 carbon atoms. The acids are further characterized by having at least one carbon to carbon double bond. Specific acids classified within this category include: oleic, linoleic, linolenic, ricinoleic, and mixtures thereof. Also suitable are the mixed acids found in tall, castor, corn, cottonseed, linseed, olive, peanut, rapeseed, safflower, sesame, and soybean oils. A mixture of carboxylic acids particularly suitable for use in our invention is that available commercially as tall oil fatty acids under the trademark Unitol ACD. A typical analysis of this product is as follows:

Table 1 Speeifi- Typical cation analysis range Fatty acids, pct 98. 8-99. 7 98. 9 Rosin acids, pct- 0.2- 0.6 0. 5 Unsapom'fiables, pct. 0. 1-0. 6 0. 6 Linoleic acid, pct 45 Oleic acid, pct 51 ,Saturated acid, pet 2. 0-2. 8 2. 4 Acid number 198-201 199 Sapcnification numb 198-202 200 Color, Gardner 3--4 3+ Viscosity:

SSU, 100 F 105 Gardner seconds 0.9 Specific gravity, F./60 F 0.905 Titre, C 0.0 Flash point, F 375 Fire point, F 435 The amounts of each of the two components making up the active ingredients of the corrosion inhibitor compositions may vary from 20 to parts of the alkali metal salt of Z-mercaptobenzothiazole admixed with 20 to 80 parts of the N,N-dimethylamide of the carboxylic acid. Somewhat better results are attained when the ratio of the two components making up the corrosion inhibitor varies from 40 to 60 parts of the former and 40 to 60 parts of the latter. Parts as used above, in the following examples, and in the appended claims, are parts by weight.

When the corrosion inhibitor composition of our invention is used in conjunction with a Fourdrinier papermaking machine, it may be added to the aqueous fluids circulating in the machine in such a quantity so as to maintain a concentration of the inhibitor of at least 0.5 to parts per million. An equivalent quantity of the inhibitor (0.5 to 100 parts of inhibtor per million parts of well fluids) is also suitable for use in water-flood operations. Larger quantities of the inhibitor may be used, but such is not desirable because costs are increased thereby with no corresponding beneficial results.

When the corrosion inhibitor is added to the water shower system, the concentration employed is usually higher and will vary from 5 to 5000 parts per million of the shower water used.

In another application, the manufacturer of the Fourdrinier wire cloth or the users may employ these compositions to impart a coating on the wires to furnish protection and corrosion resistance during shipping and storage. The treatment may be accomplished by spraying or dipping the, wire cloths, using a solution where the concentration of the inhibitor therein may be as high as 5 percent.

For convenience and ease in handling, the corrosion inhibitor composition is generally marketed as a solution of the two active components, the alkali metal salt of 2- mercaptobenzothiazole and the N,N-dimethylamide in one or more inert solvents, wherein the amount of the two active components varies from 40 to 70 parts and that of the solvent varies from 30 to 60 parts. A specific example of a solution particularly suitable for marketing comprises about 30 parts potassium 2-mercaptobenzothiazole, about 30 parts N,N-dimethylamides of tall oil fatty acids, about 30 parts water, and about 10 parts hexylene glycol. In addition to water and hexylene glycol other suitable solvents include the aliphatic alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone; glycols, as for example, ethylene glycol, diethylene glycol, and hexylene glycol; and glycol ethers such as the methyl and ethyl ethers of ethylene and. e ylene/ Concentration in test solutions, parts of tall oil fatty acids.

glycol. One purpose of the hexylene glycol in the foregoing solution is to insure a stable solution at low temperatures. As will be obvious to those skilled in the art, the alcohols and the other glycols listed may be used for this purpose with equal facility.

In order to disclose the nature of the present invention still more clearly, the following illustrative examples will be given. It is to be understood that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims.

EXAMPLE 1 Fourdrinier wire samples were cut into /3 in. x in. pieces, washed withpetroleum ether and dried under vacuum; The dry samples were then Weighed to 0.01 mg. with a semi-micro balance and each was immersed in 100 ml. of a solution containing 250 parts per million of a combination of potassium 2-mercaptobenzothiazole and N,N-dimethylamides of tall oil fatty acids. The analysis of the tall oil fatty acids used to prepare the mixture of N,N-dimethylamides is given in Table 1. The

parts of potassium Z-mercaptobenzothiazole and parts of Table 2 The linseed oil fatty acids used to prepare the mixture of N,N-dirnethylamides used in Example 3 contained 6 percent of pahnitic acid, 4 percent of stearic acid, 22 percent of oleic acid, 17 percent of linoleic acid and 51 percent of linolenic acid.

EXAMPLE 5 The same procedure that was used in Example 1 was followed with compositions containing potassium 2-mercaptobenzothiazole and N,N-dimethylamides of sperm oil fatty acids. The sperm oil fatty acids used to prepare the amide mixture contained 8 percent oleic acid, 12 percent of arachidonic acid, and 80 percent of erucic acid.

The results were not similar to those obtained in Ex ample '1. The protective coating obtained with potassium Z-mercaptobenzothiazole was very slight but the amount of coating increased with an increased concentration of dimethylamide so that the composition with 90 parts of N,N-dimethylamides of sperm oil fatty acids to 10 parts of potassium 2-mercaptobenzothiazole gave the greatest amount of protective coating. The N,Ndi'- methylamides alone also gave a significant amount of-protective coating.

EXAMPLE 6 In this example wire samples were treated as described in Examples 1 to 4 with the same combinations and amounts of potassiumZ-mercaptobenzothiazole and N,N- dimethylamides of tall oil fatty acids, oleic acid, linseed oil fatty acids, and linoleic acid. The wires were then placed in 100 ml. of a sodium hydrosulfide solution 'containing 3 parts per million of sulfide and the pH adjusted to 5.0, 6.5, or 8.0 with either aluminum sulfate orsodium hydroxide solution. The samples were main- [Weight gain of Fourdrinier wire strips after treatment with solutions containing 250 p.p.n1. of corrosion inhibitor compositions] per million:

Potassium Z-mercapto-b e n z o thiazole 250 225 200 175 150 125 100 75 50 25 [J N,N-dimethylamides of tall oil fatty acids 0 25 50 75 100 125 150 175 200 225 250 Parts in active ingredients portion of test solution:

Potassium 2-mercapto-b e n z o thiazole 100 90 80 70 60 50 V 40 20 10 o N,N-dimethylamides of tall oil fatty acids. 0 10 20 30 7O Gain in weight in milligrams pH 5.0 .82 0.67 1. 35 4. 71 5. 95 6.76 4. 83 0.21 0. 24 0.96 1. 76 pH 6.5 .34 0.72 1.96 4.08 4. 61 6. 24 4. 39 4. 80 l. 55 l. 20 0. 44 pH 8.0 23 1.10 3. 45 5 88 7. 55 9. 70 4. 11 3. 66 2. 64 2. 06 0. 37

very eifective in providing protective coatings for the wires. Solutions containing from 40 to 60 parts of potassium 2-mercaptobenzothiazole and 40 to 60 parts of the N,N-dimethylamides of tall oil fatty acids were most effective in providing protective coatings for the wires.

EXAMPLES 2 TO 4 The procedure of Example 1 was repeated in each of these. examples with the exception that N,N-dimethyloleamide, N,N-dimethylamides of linseed oil fatty acids, and N,N-dimethyllinoleamide were used in Examples 2, 3, and 4, respectively, instead of the N,N-dimethylamides The results were similar to those obtained in Example 1.

EXAMPLE 7 The effectiveness of our compositions in inhibiting the corrosion of steel was determined by comparing the weight loss of a steel test coupon subject to corrosion conditions in the presence of the inhibitor composition to the weight loss of a similar steel test coupon subject to the same corrosion conditions in the absence of the inhibitor.

The test procedure was as follows: Dry soft drink hottles were each charged with ml. of fresh brine solution obtained from a source well immediately prior to use. During the addition of the brine'so'lution to the bottle, a nitrogen blanket was maintained over the brine to prevent contact with air. Different amounts of the corrosion inhibitor composition were then added to the bottles to provide concentrations of 0, 6, and 12 parts per million of the inhibitors consisting of approximately equal parts by weight of potassium Z-mercaptobenzothiazole and the N,N-dimethylarnides of tall oil fatty acids. A /2 in. x 7% in. x in. sandblasted steel shim stock coupon (cleaned and weighed) was then placed in each bottle and each bottle sealed with a new cap. The bottles were then mounted on a wheel in such a manner that the bases of the bottles were at the circumference with the caps pointing toward the center of the wheel.

After all the bottles were mounted on the wheel, the entire apparatus was placed in an air oven which was maintained at 90 F. The wheel was rotated for a period of 24 hours. The metal coupons were removed from the bottles, cleaned, and weighed to determine the loss in weight.

The inhibitor composition afforded a substantial degree of protection to the steel coupons. The effectiveness was comparable to that obtained with such widely used corrosion inhibitors as long chain amines and diamines and imidazolines. In addition, the compositions containing alkali metal salts of Z-mercaptobenzothiazole and N,N- dimethylamides of long chain unsaturated carboxylic acids possesses other desirable properties in comparison to the commonly used corrosion inhibitors. For example, amines andldiamines are very reactive compounds and are incompatible with many other materials present in industrial systems requiring corrosion protection. Imidazolines are subject to cleavage of the ring structure by alka lies. In comparison, the compositions of this invention are stable and relatively unreactive.

The N,N-dimethylamides referred to in the examples can be prepared by the usual methods described in the literature. In these synthetic procedures, fatty acids are converted to acyl chlorides by the action of phosphorus trichloride, phosphorus pentachloride or thionyl chloride. The acyl chlorides are then reacted with dimethylamine to form the amides. In another procedure, fatty acids are heated to approximately 200 C. and an excess of dimethylamine is bubbled into the reaction vessel. Ex-

cess amine and water of reaction are removed by distillation and the procedure is continued until the reaction is complete. The dimethylamides may be purified by fractional distillation, but this is not necessary when the products are used as corrosion inhibitors in the manner herein described.

The dimethylamides of the shorter chain saturated acids are liquids and could be used in combination with alkali metal salts of Z-mercaptobenzothiazole. Arnides prepared from these acids do not afford the same degree of protection as amides prepared from the unsaturated acids with 18 carbon atoms. Saturated acids with chain lengths up to 22 carbon atoms can also be used but these amides are not so effective as our preferred amides. Furthermore, amides prepared from the longer chain saturated acids are solids which are difiicult to formulate.

Amines other than dimethylamine can be used to prepare amides of fatty acids by the procedures described above. Amides so prepared from primary and longer chain dialkyl secondary amines are not as effective as the N,N-dimethylamides of our invention when used as one of the components of the corrosion inhibitor com position.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not so limited, since many modifications may be made thereto. When the inhibitor compositions of our invention are used in waterflood systems, it may be advisable to use these compositions in conjunction with a bactericide. For further information regarding the use of bactericides in the treatment of flood water for secondary recovery, reference is made to US Patent 2,839,- 467 issued June 17,' 1958 to Charles Bryce Hutchison et al., and to the references listed in that patent regarding that subject. Other uses for our corrosion inhibitor will be apparent to those skilled in the art. It is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

The invention having been described, what is claimed and desired to be secured by Letters Patent is:

1. A corrosion inhibiting composition comprising 20 to 80 parts of an alkali metal salt of Z-mercaptobenzothiazole and 20 to 80 parts of an N,N-dimethylamide ofa straight chain carboxylic acid characterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond. 1

2. A corrosion inhibiting composition comprising 40 to parts of an alkali metal salt of Z-mercaptobenzothiazole and 40 to 60 parts of an N,N-dimethylamide of a straight chain carboxylic acid characterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond.

3. The corrosion inhibiting composition of claim 1 wherein the alkali metal salt of Z-mercaptobenzothiazole is the potassium salt of Z-mercaptobenzothiazole.

4. The corrosion inhibiting composition of claim '1 wherein the alkali metal salt of 2-mercaptobenzothiaz0le is the sodium salt of 2-mercaptobenzothiazole.

5. The corrosion inhibiting composition of claim 1 wherein the straight chain carboxylic acid is a mixture of straight chain carboxylic acids containing 18 carbon atoms and at least one carbon tocarbon double bond.

6. The corrosion inhibiting composition of claim 1 wherein the carboxylic acid is a mixture of acids derived from tall oil.

7. The corrosion inhibiting composition of claim 1 wherein the carboxylic acid is a mixture of acids derived from linseed oil.

8. The corrosion inhibiting composition of claim 1 wherein the N,N-dimethylamide is N,N-dimethyloleamide.

9. The corrosion inhibiting composition of claim 1 wherein the N,N-dimethylamide is N,N-dimethyllinoleamide.

10. The corrosion inhibiting composition of claim 1 wherein the N,N-dimethylamide is N,N-dimethyllinolenamide.

11. A corrosion inhibiting composition comprising an inert solvent in which is dissolved a mixture comprising 20 to 80 parts of an alkali metal salt of Z-mercaptobenzothiazole and 20 to parts of an N,N-dimethylamide of a straight chain carboxylic acid characterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond.

12. The corrosion inhibiting composition of claim 11 wherein the parts of the mixture comprising an alkali metal salt of Z-mercaptobenzothiazole and the N,N-dimethylamide vary from 40 to 70 parts and the parts of the inert solvent vary from 30 to 60 parts.

13. The corrosion inhibiting composition of claim 11 wherein the mixture comprises about 30 parts of the potassium salt of Z-mercaptobenzothiazole and about 30 parts of the N,N-dimethylamides of a mixture of acids derived from tall oil and the inertsolvent comprises about '30 parts of water and about 10 parts of hexylene glycol.

14. A method for inhibiting corrosion of a copper alloy normally corrodible in an aqueous medium which comprises adding to said aqueous medium a corrosion inhibiting composition comprising 20 to 80 parts of an alkali metal salt of 2-mercaptobenzothiazole and 20 to 80 parts of an N,N-dimethylamide of a straight chain carboxylic acidcharacterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond in an amount sufiicient to provide a concentration of said corrosion inhibiting composition in said aqueous medium of at least 0.5 part per million.

15. A process for the production of paper in which an aqueous fluid containing cellulosic pulp and other papermaking ingredients is circulated in contact with a Fourdrinier wire cloth composed of strands of copper containing alloys that are normally subject to mechanical wear and corrosion, whereby the useful life of such wire may be increased, which comprises adding to aqueous fluids with which the said wire cloth comes into contact a mixture comprising 20 to 80 parts of an alkali metal salt of Z-mercaptobenzothiazole and 20 to 80 parts of an N,N-dimethylamide of a straight chain carboxylic acid characterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond in an amount sufficient to provide a concentration of said corrosion inhibiting composition in said aqueous medium of at least 0.5 part per million.

16. A process comprising adding to the aqueous fluids of a papermaking machine system that includes a Fourdrinier Wire cloth the strands of which are composed of copper containing alloys a mixture comprising 20 to 80 parts of an alkali metal salt of 2-mercaptobenzothiazole and 20 to 80 parts of an N,N-dimethylamide of a straight chain carboxylic acid characterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond in an amount suificient to provide a concentration of said corrosion inhibiting composition in said aqueous medium of at least 0.5 part per million.

17. A process for the treatment of a Fourdrinier Wire cloth composed of copper containing alloy strands which comprises contacting said cloth with an aqueous solution containing at least 5 parts per million of a mixture comprising 20 to parts of an alkali metal salt of 2-mercaptobenzothiazole and 20 to 80 parts of an N,N dimethylamide of a straight chain carboxylic acid characterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond.

18. A method of reducing the corrosiveness to ferrous metals of a corrosive aqueous fluid which comprises introducing into said fluid a corrosion inhibiting amount of a mixture comprising 20 to 80 parts of an alkali metal salt of Z-mercaptobenzothiazole and 20 to 80 parts of an N,N-dimethylamide of a straight chain carboxylic acid characterized in that said acid contains 18 carbon atoms and at least one carbon to carbon double bond.

19. The corrosion inhibitor composition of claim 1 wherein the carboxylic acid is a mixture of acids derived from soy bean oil.

References Cited by the Examiner UNITED STATES PATENTS 2,708,660 5/55 Jolly 10614 2,805,135 9/57 Bell et a1 252392 3,150,035 9/64 Eddy 162-199 ALEXANDER H. BRODMERKEL, Primary Examiner. 

1. A CORROSION INHIBITING COMPOSITION COMPRISING 20 TO 80 PARTS OF AN ALKALI METAL SALT OF 2-MERCAPTOBENZOTHIAZOLE AND 20 TO 80 PARTS OF AN N,N-DIMETHYLAMIDE OF A STRAIGHT CHAIN CARBOXYLIC ACID CHARACTERIZED IN THAT SAID ACID CONTAINS 18 CARBON ATOMS AND AT LEAST ONE CARBON TO CARBON DOUBLE BOND.
 15. A PROCESS FOR THE PRODUCTION OF PAPER IN WHICH AN AQUEOUS FLUID CONTAINING CELLULOSIC PULP AND OTHER PAPERMAKING INGREDIENTS IS CIRCULATED IN CONTACT WITH A FOURDRINIER WIRE CLOTH COMPOSED OF STRANDS OF COPPER CONTAINING ALLOYS THAT ARE NORMALLY SUBJECT TO MECHANICAL WEAR AND CORROSION, WHEREBY THE USEFUL LIFE OF SUCH WIRE MAY BE INCREASED, WHICH COMPRISES ADDING TO AQUEOUS FLUIDS WITH WHICH THE SAID WIRE CLOTH COMES INTO CONTACT A MIXTURE COMPRISING 20 TO 80 PARTS OF AN ALKALI METAL SALT OF 2-MECRAPTOBENZOTHIAZOLE AND 20 TO 80 PARTS OF AN N, N-DIMETHYLAMIDE OF A STRAIGHT CHAIN CARBOXYLIC ACID CHARACTERIZED IN THAT SAID ACID CONTAINS 18 CARBON ATOMS AND AT LEAST ONE CARBON TO CARBON DOUBLE BOND IN AN AMONT SUFFICIENT TO PROVIDE A CONCENTRATION OF SAID CORROSION INHIBITING COMPOSITION IN SAID AQUEOUS MEDIUM OF AT LEAST 0.5 PART PER MILLION. 